First off, Welcome to the forum!!
Now to copy and paste...
The SP breaker is tripping for the simple reason you have an overload condition with the slide in, most likely caused by the cable being pinched. A loose connection cannot draw more current, only less... unless it is so loose it is touching something it is not suppose to, then that is a short. It needs to be checked pronto! Not later... then we can address the other problem
Good luck!